An aphorism is a short, contained statement purporting to proffer a truth. Contemporary aphorisms are often just a sentence or two, usually witty or memorable, but in Bacon’s time the word had a broader meaning and could be a short summary of an argument or observation. Hippocrates first used the term in the 5th century BCE, presenting a tract on medicine through a series of aphorisms. This set a precedent for aphorisms’ use in writing up information or arguments in scientific and philosophical fields. Bacon presents his Novum Organum as a series of aphorisms, with the exception of the Preface.

An axiom refers to a principle or conclusion asserted to be true. Bacon is concerned with axioms of different sizes: Small ones might summarize specific observations into a pattern, whereas big ones might resemble broad theories or first principles. Bacon sees axioms as synonymous with knowledge in his famous connection of knowledge and power, with “effects” representing the power part: A true axiom will allow one to produce an effect or, in other words, to manipulate the real world.